<!DOCTYPE html>
<html>
<head>
    <meta charset="utf‐8">
    <title>Hello World!</title>
</head>
<body>
Hello ${qr.subject}! ${qr.body} ${rc.contextPath}
<#if qr.subject??>
    存这个这个内容
</#if>

${RequestParameters['appId']!'不存在'}
</body>
</html>